The purpose of this research project is to study the process of fibroblast-mediated connective tissue healing, and to determine how specific alterations in the extracellular environment alter this process. The medical importance of this project is exemplified by the clinical problem of the ruptured human anterior cruciate ligament (ACL), a tissue which fails to heal after rupture. The overall goal of this work is to investigate the interactions between the fibroblasts of the human ACL and a collagen-glycosaminoglycan(CG) scaffold that might ultimately be employed as an implant to bridge between the ends of the ruptured ACL and facilitate its healing after injury. The specific aim is to quantify the effects of four different growth factors and four collagen based substrates on features associated with the repair processes in connective tissues which successfully heal: fibroblast migration, proliferation, and type I, II and III collagen synthesis. An initial pilot study has demonstrated that fibroblasts in the ruptured ACL are able to migrate from their native extracellular matrix into a 3-D collagen-glycosaminoglycan (CG) scaffold in vitro. However, the migration rates were slow, and after 4 weeks in culture, only small areas in the scaffold contained a density of cells similar to that in the unruptured human ACL. This project attempts to improve the rates of migration, proliferation, and type I collagen synthesis of ACL fibroblasts by altering the degree and type of crosslinking of the scaffold and by adding four different growth factors to the scaffold. The long term goal for this project is to define the effects of specific environmental modifications on the ability of the human fibroblast to heal dense connective tissues.